This invention relates to a hemostasis valve used in conjunction with a cannula to position and manipulate intravascular catheters of the type typically used in angiography or angioplasty procedures. Angiography is a well known and very valuable procedure used in the diagnosis of vascular and organ disease. Angioplasty has, in recent years, come into its own as a viable method for treating blockages in the coronary arteries. Both of these procedures involve inserting a catheter into one of the major arteries or veins and then advancing it into smaller branching vessels.
One prior art technique for inserting such catheters is known as the "cut down" method. This method involves surgically opening of vein or artery and inserting the catheter directly through the incision. This method is not preferred because it inevitably involves the loss of blood through the incision. This procedure also requires, in nearly all instances, venus ligation and arterial repair.
More recently, physicians have adopted an alternative procedure which includes placing a percutaneous sheath, called an introducer, into the blood vessel. A guide wire is then passed through the introducer and advanced up the artery or vein to the area to be studied or treated. Once the guide wire is in place, a catheter is inserted through the introducer and over the guide wire until the catheter working end reaches the treatment or study site.
A recognized problem with this latter technique is excess bleeding and the possibility of air embolisms, particularly during the insertion, removal or change of catheters. To reduce the possibility of excess loss of blood and/or the development of air embolisms, many attempts have been made to develop a suitable hemostasis valve or gasket for use in conjunction with the introducer. U.S. Pat. No. 4,000,739, issued on Jan. 4, 1977 to Robert C. Stevens, discloses a gasket system which is intended to inhibit excess bleeding and prevent the development of emboli. This system involves the use of two disk like gaskets formed from an elastomeric material. The first gasket has a round hole through its center and the second gasket has Y-shaped slit through its center. When stacked face-to-face, these gaskets cooperate to close the passage about the catheter during insertion and during manipulation of the catheter. Following removal of the catheter, the Y-shaped slit closes to prevent blood air from flowing therethrough.
U.S. Pat. No. 4,436,519, issued on Mar. 13, 1984 to William J. O'Neil, discloses a dome-shaped hemostasis valve which is directed to these same problems. This valve has a body comprised of a central passage and a resilient dome-shaped diaphragm having a wall member with a single linear slit. A dome-shaped diaphragm is used because it will act in cooperation with the walls of central passage to resiliently urge the slit closed when no catheter is present therethrough.
Still another valve arrangement is disclosed in U.S. Pat. No. 4,626,245 to Weinstein. This patent discloses an elastomeric partition valve of one piece construction. The valve includes a first slit defined by one side of the partition valve and a second slit defined by the opposite side. Each slit has a location which creates two spaced apart points of intersection with the other slit. The Weinstein Patent further indicates that the first and second slit should both have a Y-shape.
While each of the designs discussed above have certain advantages, none of them are deemed to be fully satisfactory. For example, each permits a certain amount of blood leakage because they do not provide a sufficiently tight seal when only the guide wire is in place. This is particularly true for smaller diameter guide wires.